RADIATION HARDNESS OF POLYCRYSTALLINE DIAMOND

Undoped and B-doped polycrystalline diamond films have been irradiated with 2-MeV alpha particles and 3-MeV protons at doses ranging from D= 10(12) to D=10(17) cm(-2). The radiation damage has been studied using conductivity measurements and Raman/photoluminescence spectroscopy. F or undoped diamond films, the H3 luminescent center (N-V-N) is detecte d around 2.45 eV for D greater than or equal to 10(14) He+ cm(-2). The diamond peak broadens and shifts to lower wavenumbers for D greater t han or equal to 10(16) He+ cm(-2), indicative of the appearance of cry stalline defects and tensile stress. No graphite is detected. On the c ontrary we observe an annealing of the as-grown sp(2) defects as evide nced by a decrease in the intensity of the Raman band at 1500 cm(-1) a fter irradiation. At D=3 x 10(16) He+ cm(-2) we observe two new defect peaks at 1496 and 1635 cm(-1). The I(VsT) characteristics of the undo ped samples remain unaffected up to D=10(16) He+ cm(-2). For D=3 x 10( 16) He+ cm(-2) the conductivity increases drastically and the I(T) cha racteristics show the presence of irradiation defects at 0.3-0.4 eV. S imilar phenomena are observed after H+ irradiation, but for doses 100 times higher. Less damage is detected by Raman spectroscopy in the B-d oped films, The conductivity of these films decreases as a result of H e+ and H+ irradiation. The activation energy decreases after He+ irrad iation, and increases after Ht irradiation. The latter case correspond s to the compensation of the boron acceptor level by irradiation defec ts. (C) 1997 Elsevier Science S.A.